The invention relates to a device for controlling a liquid flow.
The invention furthermore relates to a gas pressure delivery system for use in a device according to the invention.
Usually a mechanical device, such as a valve, a stop valve, a flow controller or a level controller is used for controlling a liquid flow.
One drawback of the use of such a mechanical device is that in the long run it will not operate properly anymore, due to the deposition of dirt or due to corrosion. Deposited dirt will prevent a valve from shutting off properly, and a flow controller will regulate a flow other than the desired flow. Corrosion may cause pivots to get stuck or packings to become rust-bound, as a result of which the valves in which said pivots or packings are present will no longer operate properly. Also wear may prevent mechanical devices from operating properly. Mechanical devices are liable to malfunction, therefore, and require a great deal of maintenance. This is problematic in particular when said devices form part of systems which are not easily accessible, such as sewage systems or pipes under dikes. In those cases repairs are often difficult to carry out, are time-consuming and costly. Furthermore, mechanical devices are expensive. Especially large devices, such as weirs, which up to now required large and heavy movable liquid-retaining constructions, which necessitated the use of heavy-duty control elements are expensive.
One object of the invention is to provide a device for controlling a liquid flow which requires very little maintenance, which is reliable and easy to operate, and which is preferably inexpensive.
The device according to the invention is characterized in that the device is configured such that a liquid flow being passed through the device during operation can be controlled by means of a gas pressure.
Hardly any moving part is required, if at all, because a gas pressure is used for controlling the liquid flow, as a result of which the device requires little maintenance and is not very liable to malfunction.
The invention is based on the insight that a gas is capable of displacing a liquid. The through-flow can be increased, reduced or stopped by locally introducing or discharging a gas into or from a predetermined part of a liquid pipe.
One embodiment of the device according to the invention comprises a bent pipe portion. Said pipe portion is preferably disposed in the device in such a manner that the bend in said pipe portion is positioned higher than the rest. Thus there is a higher portion, in which a gas may be present. Gas is lighter than liquid, and will thus rise in liquid. An atmospheric pressure, an underpressure or an overpressure may prevail in said bend. The ends of the pipe portion may be disposed in different reservoirs, for example, enabling to control a liquid flow between said reservoirs.
Another embodiment of the device according to the invention has a pipe portion which comprises more than one bend, so that it forms a system of communicating vessels. This makes it possible to control the liquid with extra precision. This device may be suitably incorporated in a system of pipes. The length of the various parts of the system of communicating vessels may be adapted to the dimension and the vertical position of the pipes of the system in which the device is incorporated, as a result of which the desired shutting-off action and flow control can take place with extra precision. This embodiment of the device according to the invention can be realised in several manners. Most of said manners will result in a device which is not dependent on energy being supplied.
Another embodiment of the device according to the invention comprises a bent pipe portion, which comprises a wall in which an opening is present, through which opening a gas can be introduced or carried off. This provision enables an even better control of the liquid flow. The gas pressure that is applied can be adapted to the dimensions and the location of the pipes of the system in which the device is incorporated.
The gas pressure is preferably delivered by means of a gas pressure delivery system which is controlled by means of a liquid flow. In that case the system will comprise few moving parts, as a result of which the system requires little maintenance and is not very liable to malfunction and is practically independent of the supply of energy. The gas pressure delivery system may for example comprise a container which is in open communication on one side with a liquid reservoir (which may also form part of a pipe) in which the level of liquid can be varied. In such a manner a pressure can be generated. The container contains gas during operation and, as already said before, it is in open communication with a liquid reservoir and, on the side where no liquid is present, with a pipe whose diameter is much smaller than that of the container. When the level of the liquid in the liquid reservoir rises, gas will be carried off through the pipe. As a result of the difference in diameter between the container and the pipe, a relatively small rise of the liquid level will result in a large amount of gas being carried off. The advantage of such a system is that it is simple to install. The flow through the pipe determines the gas pressure that is generated.
In another embodiment of said gas pressure delivery system the container is shut off from the pipe by means of one or more spring-suspended plates. This has the advantage that no liquid can find its way into the gas pipe.
In another embodiment two plates are present, one plate having a larger area than the other, which plates are interconnected. Preferably said plates are rigidly interconnected. One advantage of this embodiment is the fact that a relatively small pressure on the larger plate is capable of compensating a relatively large pressure on the smaller plate. This makes it possible to generate a large gas pressure by means of a small increase of the flow through the pipe.
According to another embodiment of the device according to the invention the gas pressure is delivered by a compressor. The advantage of this is that thus practically any gas pressure that is desired can be delivered in a simple manner.
According to another embodiment of the device according to the invention a float system is used for opening and closing openings for the supply and discharge of gas. A float is an object which is capable of floating on a liquid surface. In one embodiment of the device according to the invention a float thus floats on the surface of the liquid whose level or flow is to be controlled during operation. The float is connected to a valve, which is capable of opening or closing an opening through which a gas can be supplied or discharged. The liquid level determines whether the opening will be open or closed. The liquid level is influenced by supplying or discharging gas. In this manner it is possible to control the liquid level or the liquid flow. The device may comprise more than one float, with each float controlling a separate opening. The opening or closing of the various openings serves different purposes.
The device according to the invention can be used advantageously for controlling liquid flows in a sewage system. With this type of system there is a great risk of dirt being deposited, since the system is used for carrying off dirt. Moreover, a sewage system is very difficult to gain access to, because it is located deep under the ground surface. The device according to the invention exhibits hardly any fouling, since there is hardly any deposition of dirt, and furthermore it requires almost no maintenance. This makes the device according to the invention highly suitable for this use. The device may for example be used for protecting against backflow in a sewage system in a cellar, for limiting the flow in sewage chains, and for separating rain water into highly polluted rain water and less polluted rain water. Said rain water may be discharged separately to a foul sewer and a clean sewer respectively.
The device according to the invention can also be used advantageously for controlling a liquid flow between liquid basins, such as the water basins of a water purification plant. In an embodiment according to the invention which is highly suitable for this purpose the bent pipe portion comprises two spaces on either side of a wall. The gas pressure in the space above the wall can be varied, as a result of which it is possible to vary the amount of water that flows over the water from one space into another. The device may furthermore be configured such that a basin which is in communication with said one space can be emptied, whilst a basin which is in communication with the other space may remain full. This is usefull in particular when maintenance work must be carried out on a basin. The device according to the invention thus enables to carry out maintenance work on basins in which heavy-duty valves, which require a great deal of maintenance, are avoided.
The device according to the invention is also highly suitable for controlling liquid levels and liquid flows in hydraulic-engineering works and irrigation works. The usual engineering works, such as weirs, drainage sluices and tidal barriers comprise heavy, expensive, movable structures requiring a great deal of maintenance. The control installations of these structures are large, complex and dependent on the supply of energy. The device according to the invention does not comprise any movable structures or control installations, which enables a more reliable and inexpensive control of liquid levels and liquid flows. Furthermore it is possible, if the device is not too large, to use an automatic control system which does not depend on the supply of electric energy. An example of a hydraulic-engineering work wherein the device according to the invention can be used advantageously is an installation for controlling a liquid flow under a dyke. Pipes under dykes are not easily accessible. For that reason it is important that the installations that are used do not require a great deal of maintenance.
According to another embodiment the device is spiral-shaped. The advantage of this embodiment is that it provides a better through-flow during operation.